A group of three players had been going through my campaign for a year and a half, when a fourth player was added around level 15.
The new player entered in media res: there was a ton of back story, more than a hundred NPCs and the rest of the group was running from one important quest to the next.

Unfortunately, I made a huge mistake in the way this character entered the campaign: he was scooped up from the Nine Hells and brought to the group's home world to assist them in a battle that won't take place for at least another 7 levels.

The thing is, neither the player nor his character has any stake in this world. They don't know any people/NPCs there, they don't know the history or the intricacies of the quests and their relationship with the rest of the party is strained at best. Because the character is unaligned, he's not even that interested in helping the party defeat the big bad.

At the moment, while the rest of the players talk to NPCs (both old and new), remember history, important clues and back story and discuss what quests to focus on, the new guy sits quietly in the corner and waits because he has no reason to do any of those things.

What are some good ideas to get this player AND his character engaged in the story and/or just help him have fun?

Note: The player is not at all disinterested - he seems to find the story interesting and wants to play with us. However, I understand why he would be unmotivated with the (in retrospective, bad and irreversible) way he was added.

7 Answers
7

I was in a similar situation a couple of years ago, in the role of the newly-come player. The party, all around 20th level and with a couple of years of familiarity with the world, had found my new character embedded in magical rock and awakened me deep inside a Drow city. Now, the DM had to work on integrating me with the party and with the world.

There were several things we did to help:

Link to other PCs. Apparently one of the PCs had a side-quest a couple of months earlier where he travelled a few thousand years to the past. The DM used that to link my character to him, with some out-of-character agreement between the players to add our acquaintance to our backstories. It made sure my character wasn't too out of touch, since at least I had one person I knew in this alien world.

One of the first things that happened after I joined the group was that I came into possession of a certain item, a little gem-covered pyramid I swiped "as my retirement fund". This ended up being an artifact with a lot of importance for the rest of the plot, so, again, a lot of NPCs wanted things to do with me.

The Big Bad, or at least some intermediate Big Bad, turned out to be linked to my character's past. This really got me more involved with things.

In addition to these tactics, you should also talk to the player. While it's true that a lot of the job of integrating the character is your job, as GM, it is still also the player's job to fit into the party. Roleplaying is a social activity, and if the player isn't here to socialize, he's doing something wrong. I don't believe in blindly adhering to character concepts at the expense of party dynamics.

Think outside the box. Don't be blindly adherent to your grand vision of the plot. You haven't told us anything about his motivation or why he got "scooped," but change/add quests so that he/his faction/his whatever (family/race/etc) does have some kind of stake in them instead of expecting him to get on the railroad train heading to Cleveland. Also - if you screwed up with seven levels to go, and can't figure out how to incorporate the new PC fully for some reason, make a change. Have him bail on that character and bring in another; have him take over an existing NPC he likes, etc. Every day you perpetuate the mistake, you're making it again afresh, it is not irreversible in practice. Have Hellboy betray the party and the new player play a paladin who saves their bacon, for instance. He does have to change characters which is sad but can't be too invested in the character yet, apparently... See next point.

If the PCs are interacting with new NPCs, why isn't he? He lives there now... That sounds like a player needs to stop sitting on his hands problem. Whatever these NPCs did to make them important to the rest of the PCs, why is that not starting to take root with the new guy? Why does he not care about any of the quests, even from the point of view of I need to protect these guys or I will get phat magical lewt? This is clearly a player problem, he's not really identifying with whatever Hellboy he is and working proactively to achieve his goals. It's OK if those goals are irrelevant to what the party's doing, in fact it's more interesting that way. He can sweat them to come with him on a quest since he's doing a lot of vice versa. Talk with the player and just say "hey man you need to get more proactive about pursuing your character's goals."

Talk to the other players. Are they not giving a damn? When we get a new PC in the group (just like when a new person joins a work group or whatever IRL) the existing ones can make a big effort to include them, introduce them, say "what do you think..." It sounds like you mainly care about your plot and all your players just care about their own character and no one's doing much to facilitate each others' fun in an interactive way.

He was scooped up out of the Nine Hells by...? A god who wants to assist the party, presumably. Also presumably, a god with some interest in this character. There's scope for inquisitive minds there; perhaps when they go to the temple to inquire, the high priest provides an item that has been waiting a hundred years for the Chosen One who will need it. Change the attitude from 'What have I got to do with these people?' to 'A god thinks I am closely involved with these people; let me find out how.'

I would suggest something a little similar to @CatLord - have the new player write some backstory material about his character. Work with the new guy, providing plot points and campaign setting information for his backstory. Level 15 affords a lot of ground for backstory information, and having an origin in the Nine Hells (whether he was native to there or not) begs for a good story explaining the how and why he came from there.

There are a few purposes for developing this character's backstory.

As any character's background information does, it provides depth to the character. The deeper the character, the more invested and hopefully entertained and interested the player is about his character. This can manifest directly during gameplay, eliminating a lot of "why should my character care about this situation or NPC?" Well, there may be all sorts of reasons related to the character's history as to why the character should care about a present situation.

The backstory provides the GM an opportunity to weave in plot-related points that can be leveraged in the present time as a hook to get the character involved. These hooks may not be the same straight-forward motivators that the other characters in the party have, but there may be side-angles that afford the new character an opportunity to align his interests with the party's interests.

Background information provides a cohesive foundation for the character's behavior, and that may be interesting in itself to the other characters. The other characters may start having more interest in the new guy if the new guy starts making a point of behaving consistently in a certain way. "Why are you always so standoffish with the new people we meet?" "Well, you see this scar here? That came from when I approached this stranger at a bar once, and when he pulled a knife on me for just talking with him, that was only the start of my troubles..."

No personal interest in the party and no knowledge of the world or the characters? Stop right there! That sounds like a beautiful place to inject doubt into the party. Consider how you would react in the same situation. Taken from here, Earth, and brought to a land of utterly different constructs and dynamics.

You would imprint on whomever first discovered you. You'd travel with them, learn from them, and after following for some time - you would form your own opinions of things.

This is the perfect chance for the players to reaffirm their own assumptions about what side they are on. By this level, PCs are forces of nature who can destroy whole towns, level entire civilizations in some cases, and often they will do exactly that in the course of a campaign.

As an outsider, this might be totally shocking. Perhaps the race of beings the PCs assault are pure evil, but those are still women and children being slaughtered. There is potential here to have a character that plays wonderful counterpoint to these atrocious actions, or lesser ones, and forces the party to explain why they are doing what they are doing.

By expressing their needs to a 3rd party, they reaffirm them. They prove to themselves they are on the right track. And perhaps, they can convince the new member of the need. Or perhaps not. It could be even more fun for this new person to make the party realize how terrible they've become and lead them on a path of atonement, totally throwing the plot for a loop.

My recommendation is to come up with a cheat sheet for some of the backstory. I'm assuming he hasn't been in the Nine Hells since his creation/birth, so there must be some things he knows about the mortal world to some extent. Either that, or have the party spend some time sharing a few notes they think will be pertinent to the most imminent threat(s).

I have faced similar situation several times in our 4 years long GURPS fantasy campaign.

Half year after start, a guy playing a spy joined. His goal was to find his lost brother, and he quickly found the brother was kidnapped by common enemy. The guy left the party later, but he fit in well, especially when he could use his sneaky abilities.

More than two years after start a girl joined us with a character of priestess of a death God. We made a detailed backstory, a common goal and voice of her god suggesting to join the party. Since then, I made sure to include some demons, undead or black magic (the character is one of the best exorcists in area) in every session she plays. She had no links to PCs (except for common goal with one of them) or important NPCs, but desire to rebuild her god's cult and getting powerful allies in first few sessions helped her to integrate to the party quickly.

Few months after her, a guy joined as a scout. He left after two sessions - I think he expected something more similar to dungeoncrawling than to our campaign featuring espionage and intrigue (and war too, but he joined during a winter truce in the campaign).

A year after the priestess, a guy joined as a noble, a brother of one of the party's most important allies, who just returned from a long-term diplomatic mission. He quickly became one of the leading characters in the party.

Half year after that (almost three years after start) a mage joined the group. The character's biggest goals are training and research, but adventuring with the party is the right challenge for both the player and the character. Getting accustommed with the world and and rules wasn't easy for him, but he is one of the most active players from the very start.

Half a year ago, a new guy playing scout/ranger joined. The character simply inherited the noble's agenda (he was linked to a PC of one of the new players), but he has no goals of his own. He is not a very active player and I'm afraid he wouldn't stay for long.

Now I can induce few rules (they are somewhat similar to what mwyzplk suggested):

Motivation is crucial. The character needs agenda, which is interresting for the player (optimally the player's idea) and is either common or easily joinable with the agenda of the party or at least one other PC. If the player don't recognize his character's agenda as his own or if it's not weaved into the tapestry of party's goals (after more than a year, party's goals must be complex), the player would likely leave the party, or at least they wouldn't be interrested in the game, like your new player. I guess this is where you made the mistake. Being different (as DampeS8N suggested) could help, but still it's a passive goal, so it's not as easy to motivate the player as an active character-driven goal.

Spotlight is number two. Give the character scenes where they are the best expert in the party - it motivates the player and earns the character respect of the old party members. The worst situation is when there's already a PC of the same class and higher level, but these spotlight abilities don't have to be written in character sheet - you devil from hell can have information that others can't easily learn without him. Artifact mentioned in lisardggy's answer is another good example.

Also, help the player overcome the newcomer shock. There are many details in the game world to learn and many internal jokes in the party. Tell the player as much as possible before they join and keep explaining during game. Crucial point here is whether old players are helpful, whether they try to explain party's internal jokes and other difficult things to the newbie - GM can't make all the work by themself. Our group is excellent in this aspect, but still one player left because he didn't really want to adopt party's tactics and other customs. If your old players don't try to invite the newbie and the new player is not extroverted enough, this might be the core of the problem.

What to do in your situation? Tell your players to help the newcomer and sit with the new player to find some motive he would like. Ask him, what he expects, what he would like to do. If it's not reconcilable with his character, then replace the character, but this is unlikely. Then think how to give him what he wants, and ideally to join his goals with party's.

If the player just wants to honor his character's backstory (i.e. he is a "myguyist" of some sort), just state that the archvillain is an important ally (or even a master) of a rival faction in Hells, and let the party discover a plot arranged by another hellish faction. This will teach him to pay attention to mere mortals! Or bring some old friend from Hells, who would just visit him and ask what he found about this plane of existence - tell him, that ignorance is not good, even for a Hellboy like him.

Also, NPCs should be interrested in such a character, and the interrest doesn't have to be in form of assassination or exorcism attempts. Some should be interrested in him in the positive way - another encouragement to start involving in relationships with NPCs.